2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 Marco Costalba
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
34 //// Local definitions
39 // Values modified by Joona Kiiski
40 const Value BishopPairMidgameBonus = Value(109);
41 const Value BishopPairEndgameBonus = Value(97);
43 // Polynomial material balance parameters
44 const Value RedundantQueenPenalty = Value(320);
45 const Value RedundantRookPenalty = Value(554);
46 const int LinearCoefficients[6] = { 1709, -137, -1185, -166, 141, 59 };
48 const int QuadraticCoefficientsSameColor[][6] = {
49 { 0, 0, 0, 0, 0, 0 }, { 33, -6, 0, 0, 0, 0 }, { 29, 269, -12, 0, 0, 0 },
50 { 0, 19, -4, 0, 0, 0 }, { -35, -10, 40, 95, 50, 0 }, { 52, 23, 78, 144, -11, -33 } };
52 const int QuadraticCoefficientsOppositeColor[][6] = {
53 { 0, 0, 0, 0, 0, 0 }, { -5, 0, 0, 0, 0, 0 }, { -33, 23, 0, 0, 0, 0 },
54 { 17, 25, -3, 0, 0, 0 }, { 10, -2, -19, -67, 0, 0 }, { 69, 64, -41, 116, 137, 0 } };
56 // Unmapped endgame evaluation and scaling functions, these
57 // are accessed direcly and not through the function maps.
58 EvaluationFunction<KmmKm> EvaluateKmmKm(WHITE);
59 EvaluationFunction<KXK> EvaluateKXK(WHITE), EvaluateKKX(BLACK);
60 ScalingFunction<KBPK> ScaleKBPK(WHITE), ScaleKKBP(BLACK);
61 ScalingFunction<KQKRP> ScaleKQKRP(WHITE), ScaleKRPKQ(BLACK);
62 ScalingFunction<KPsK> ScaleKPsK(WHITE), ScaleKKPs(BLACK);
63 ScalingFunction<KPKP> ScaleKPKPw(WHITE), ScaleKPKPb(BLACK);
71 typedef EndgameEvaluationFunctionBase EF;
72 typedef EndgameScalingFunctionBase SF;
74 /// See header for a class description. It is declared here to avoid
75 /// to include <map> in the header file.
77 class EndgameFunctions {
81 template<class T> T* get(Key key) const;
84 template<class T> void add(const string& keyCode);
86 static Key buildKey(const string& keyCode);
87 static const string swapColors(const string& keyCode);
89 // Here we store two maps, one for evaluate and one for scaling
90 pair<map<Key, EF*>, map<Key, SF*> > maps;
92 // Maps accessing functions for const and non-const references
93 template<typename T> const map<Key, T*>& get() const { return maps.first; }
94 template<typename T> map<Key, T*>& get() { return maps.first; }
97 // Explicit specializations of a member function shall be declared in
98 // the namespace of which the class template is a member.
99 template<> const map<Key, SF*>&
100 EndgameFunctions::get<SF>() const { return maps.second; }
102 template<> map<Key, SF*>&
103 EndgameFunctions::get<SF>() { return maps.second; }
111 /// Constructor for the MaterialInfoTable class
113 MaterialInfoTable::MaterialInfoTable(unsigned int numOfEntries) {
116 entries = new MaterialInfo[size];
117 funcs = new EndgameFunctions();
118 if (!entries || !funcs)
120 cerr << "Failed to allocate " << (numOfEntries * sizeof(MaterialInfo))
121 << " bytes for material hash table." << endl;
122 Application::exit_with_failure();
127 /// Destructor for the MaterialInfoTable class
129 MaterialInfoTable::~MaterialInfoTable() {
136 /// MaterialInfoTable::get_material_info() takes a position object as input,
137 /// computes or looks up a MaterialInfo object, and returns a pointer to it.
138 /// If the material configuration is not already present in the table, it
139 /// is stored there, so we don't have to recompute everything when the
140 /// same material configuration occurs again.
142 MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
144 Key key = pos.get_material_key();
145 int index = key & (size - 1);
146 MaterialInfo* mi = entries + index;
148 // If mi->key matches the position's material hash key, it means that we
149 // have analysed this material configuration before, and we can simply
150 // return the information we found the last time instead of recomputing it.
154 // Clear the MaterialInfo object, and set its key
158 // Let's look if we have a specialized evaluation function for this
159 // particular material configuration. First we look for a fixed
160 // configuration one, then a generic one if previous search failed.
161 if ((mi->evaluationFunction = funcs->get<EF>(key)) != NULL)
164 else if ( pos.non_pawn_material(BLACK) == Value(0)
165 && pos.piece_count(BLACK, PAWN) == 0
166 && pos.non_pawn_material(WHITE) >= RookValueMidgame)
168 mi->evaluationFunction = &EvaluateKXK;
171 else if ( pos.non_pawn_material(WHITE) == Value(0)
172 && pos.piece_count(WHITE, PAWN) == 0
173 && pos.non_pawn_material(BLACK) >= RookValueMidgame)
175 mi->evaluationFunction = &EvaluateKKX;
178 else if ( pos.pawns() == EmptyBoardBB
179 && pos.rooks() == EmptyBoardBB
180 && pos.queens() == EmptyBoardBB)
182 // Minor piece endgame with at least one minor piece per side,
184 assert(pos.knights(WHITE) | pos.bishops(WHITE));
185 assert(pos.knights(BLACK) | pos.bishops(BLACK));
187 if ( pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2
188 && pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2)
190 mi->evaluationFunction = &EvaluateKmmKm;
195 // OK, we didn't find any special evaluation function for the current
196 // material configuration. Is there a suitable scaling function?
198 // The code below is rather messy, and it could easily get worse later,
199 // if we decide to add more special cases. We face problems when there
200 // are several conflicting applicable scaling functions and we need to
201 // decide which one to use.
204 if ((sf = funcs->get<SF>(key)) != NULL)
206 mi->scalingFunction[sf->color()] = sf;
210 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
211 && pos.piece_count(WHITE, BISHOP) == 1
212 && pos.piece_count(WHITE, PAWN) >= 1)
213 mi->scalingFunction[WHITE] = &ScaleKBPK;
215 if ( pos.non_pawn_material(BLACK) == BishopValueMidgame
216 && pos.piece_count(BLACK, BISHOP) == 1
217 && pos.piece_count(BLACK, PAWN) >= 1)
218 mi->scalingFunction[BLACK] = &ScaleKKBP;
220 if ( pos.piece_count(WHITE, PAWN) == 0
221 && pos.non_pawn_material(WHITE) == QueenValueMidgame
222 && pos.piece_count(WHITE, QUEEN) == 1
223 && pos.piece_count(BLACK, ROOK) == 1
224 && pos.piece_count(BLACK, PAWN) >= 1)
225 mi->scalingFunction[WHITE] = &ScaleKQKRP;
227 else if ( pos.piece_count(BLACK, PAWN) == 0
228 && pos.non_pawn_material(BLACK) == QueenValueMidgame
229 && pos.piece_count(BLACK, QUEEN) == 1
230 && pos.piece_count(WHITE, ROOK) == 1
231 && pos.piece_count(WHITE, PAWN) >= 1)
232 mi->scalingFunction[BLACK] = &ScaleKRPKQ;
234 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) == Value(0))
236 if (pos.piece_count(BLACK, PAWN) == 0)
238 assert(pos.piece_count(WHITE, PAWN) >= 2);
239 mi->scalingFunction[WHITE] = &ScaleKPsK;
241 else if (pos.piece_count(WHITE, PAWN) == 0)
243 assert(pos.piece_count(BLACK, PAWN) >= 2);
244 mi->scalingFunction[BLACK] = &ScaleKKPs;
246 else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
248 mi->scalingFunction[WHITE] = &ScaleKPKPw;
249 mi->scalingFunction[BLACK] = &ScaleKPKPb;
253 // Compute the space weight
254 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >=
255 2*QueenValueMidgame + 4*RookValueMidgame + 2*KnightValueMidgame)
257 int minorPieceCount = pos.piece_count(WHITE, KNIGHT)
258 + pos.piece_count(BLACK, KNIGHT)
259 + pos.piece_count(WHITE, BISHOP)
260 + pos.piece_count(BLACK, BISHOP);
262 mi->spaceWeight = minorPieceCount * minorPieceCount;
265 // Evaluate the material balance
266 const int pieceCount[2][6] = { { pos.piece_count(WHITE, BISHOP) > 1, pos.piece_count(WHITE, PAWN), pos.piece_count(WHITE, KNIGHT),
267 pos.piece_count(WHITE, BISHOP), pos.piece_count(WHITE, ROOK), pos.piece_count(WHITE, QUEEN) },
268 { pos.piece_count(BLACK, BISHOP) > 1, pos.piece_count(BLACK, PAWN), pos.piece_count(BLACK, KNIGHT),
269 pos.piece_count(BLACK, BISHOP), pos.piece_count(BLACK, ROOK), pos.piece_count(BLACK, QUEEN) } };
274 for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
276 // No pawns makes it difficult to win, even with a material advantage
277 if ( pos.piece_count(c, PAWN) == 0
278 && pos.non_pawn_material(c) - pos.non_pawn_material(opposite_color(c)) <= BishopValueMidgame)
280 if ( pos.non_pawn_material(c) == pos.non_pawn_material(opposite_color(c))
281 || pos.non_pawn_material(c) < RookValueMidgame)
285 switch (pos.piece_count(c, BISHOP)) {
299 // Redundancy of major pieces, formula based on Kaufman's paper
300 // "The Evaluation of Material Imbalances in Chess"
301 // http://mywebpages.comcast.net/danheisman/Articles/evaluation_of_material_imbalance.htm
302 if (pieceCount[c][ROOK] >= 1)
303 matValue -= sign * ((pieceCount[c][ROOK] - 1) * RedundantRookPenalty + pieceCount[c][QUEEN] * RedundantQueenPenalty);
305 // Second-degree polynomial material imbalance by Tord Romstad
307 // We use NO_PIECE_TYPE as a place holder for the bishop pair "extended piece",
308 // this allow us to be more flexible in defining bishop pair bonuses.
309 them = opposite_color(c);
310 for (int pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; pt1++)
312 int c1 = sign * pieceCount[c][pt1];
316 matValue += c1 * LinearCoefficients[pt1];
318 for (int pt2 = NO_PIECE_TYPE; pt2 <= pt1; pt2++)
320 matValue += c1 * pieceCount[c][pt2] * QuadraticCoefficientsSameColor[pt1][pt2];
321 matValue += c1 * pieceCount[them][pt2] * QuadraticCoefficientsOppositeColor[pt1][pt2];
326 mi->value = int16_t(matValue / 16);
331 /// EndgameFunctions member definitions. This class is used to store the maps
332 /// of end game and scaling functions that MaterialInfoTable will query for
333 /// each key. The maps are constant and are populated only at construction,
334 /// but are per-thread instead of globals to avoid expensive locks needed
335 /// because std::map is not guaranteed to be thread-safe even if accessed
336 /// only for a lookup.
338 EndgameFunctions::EndgameFunctions() {
340 add<EvaluationFunction<KNNK> >("KNNK");
341 add<EvaluationFunction<KPK> >("KPK");
342 add<EvaluationFunction<KBNK> >("KBNK");
343 add<EvaluationFunction<KRKP> >("KRKP");
344 add<EvaluationFunction<KRKB> >("KRKB");
345 add<EvaluationFunction<KRKN> >("KRKN");
346 add<EvaluationFunction<KQKR> >("KQKR");
347 add<EvaluationFunction<KBBKN> >("KBBKN");
349 add<ScalingFunction<KNPK> >("KNPK");
350 add<ScalingFunction<KRPKR> >("KRPKR");
351 add<ScalingFunction<KBPKB> >("KBPKB");
352 add<ScalingFunction<KBPPKB> >("KBPPKB");
353 add<ScalingFunction<KBPKN> >("KBPKN");
354 add<ScalingFunction<KRPPKRP> >("KRPPKRP");
355 add<ScalingFunction<KRPPKRP> >("KRPPKRP");
358 EndgameFunctions::~EndgameFunctions() {
360 for (map<Key, EF*>::iterator it = maps.first.begin(); it != maps.first.end(); ++it)
363 for (map<Key, SF*>::iterator it = maps.second.begin(); it != maps.second.end(); ++it)
367 Key EndgameFunctions::buildKey(const string& keyCode) {
369 assert(keyCode.length() > 0 && keyCode[0] == 'K');
370 assert(keyCode.length() < 8);
375 // Build up a fen substring with the given pieces, note
376 // that the fen string could be of an illegal position.
377 for (size_t i = 0; i < keyCode.length(); i++)
379 if (keyCode[i] == 'K')
382 s << char(upcase? toupper(keyCode[i]) : tolower(keyCode[i]));
384 s << 8 - keyCode.length() << "/8/8/8/8/8/8/8 w -";
385 return Position(s.str()).get_material_key();
388 const string EndgameFunctions::swapColors(const string& keyCode) {
390 // Build corresponding key for the opposite color: "KBPKN" -> "KNKBP"
391 size_t idx = keyCode.find("K", 1);
392 return keyCode.substr(idx) + keyCode.substr(0, idx);
396 void EndgameFunctions::add(const string& keyCode) {
398 typedef typename T::Base F;
400 get<F>().insert(pair<Key, F*>(buildKey(keyCode), new T(WHITE)));
401 get<F>().insert(pair<Key, F*>(buildKey(swapColors(keyCode)), new T(BLACK)));
405 T* EndgameFunctions::get(Key key) const {
407 typename map<Key, T*>::const_iterator it(get<T>().find(key));
408 return (it != get<T>().end() ? it->second : NULL);